肺癌A549放射抗拒细胞亚系的建立及抗拒机制的研究

目的 建立肺癌细胞系A549的放射抗拒模型并探讨放射抗拒的机制。方法 应用两种方案对非小细胞肺癌A549细胞系进行X射线照射:一组照射5次,每次剂量600 cGy;另一组照射15次,每次剂量200 cGy。照射完成后对存活细胞单克隆化分别命名为A549-S1和A549-S2,采用克隆形成实验测定两种细胞亚系及亲本A549细胞的放射敏感性,流式细胞术检测细胞周期特征,RT-PCR和Western blot分别测定3种细胞Notch1的表达。结果 与亲本A549细胞相比,A549-S1细胞显示出明显放射抗性,D₀、D_q及N值增大,细胞存活曲线肩区增宽,在SF₂水平上,放射抗性是A549的1.38倍,细胞的S期比例较A549细胞明显增高, G₀/G₁期比例下降(P<0.05),Notch1的表达较A549细胞明显增强。而A549-S2的放射敏感性与亲本细胞相比稍增强,D₀、D_q及N值均减小,细胞存活曲线肩区变窄,在SF₂水平上,放射抗性是A549细胞的0.84倍,细胞S期、G₀/G₁期比例较A549细胞减少,而G₂/M期比例明显增加(P<0.05),Notch1表达与亲本A549细胞相比无明显变化。结论 A549细胞亚系放射抗拒的形成与不同照射方案有一定关系,得出的放射抗拒细胞亚系显示出与亲本不同的细胞周期特征,而细胞特征的变化可能与Notch1的表达增强有关。

Establishment of a radioresistant human lung cancer cell subline and its mechanism of radioresistance

Objective To establish a radioresistant cell subline from a human A549 lung cancer cell line and investigate the mechanism of radioresistance. Methods Two proposals were applied for the non-small cell lung cancer A549 cells irradiated with X-rays:A group of A549 cell line was irradiated five times, the fractionated dose was 600 cGy, and the other group was exposed 15 times, the fractionated dose was 200 cGy. After the completion of irradiation, two monoclones were obtained from the survival of cells and named the subline A549-S1 and A549-S2. The radiosensitivity and cell cycle distribution of these two clones,together with its parental A549 cells were measured by clone formation assay and flow cytometry.The mRNA and protein levels of Notch1 in A549 cell line and the sublines were determined by RT-PCR and Western-blots. Results Compared with the parental A549 cells, A549-S1 cells showed significant resistance to radiation with D₀,D_q and N values increased, and a broader initial shoulder as well as 1.38-fold increased value of SF₂.The A549-S1 subline also showed higher percentage of cells in S phase and G₂/M phase,but lower percentages in G₀/G₁ phase (P<0.05). The expression of Notch1 in A549-S1 was enhanced obviously than in A549 cells. But for A549-S2 the radiosensitivity was slightly increased compared with the parental cells with D₀,D_q and N values decreased and a curve initial shoulder. The ratio of cells in S and G₀/G₁ phase ratio was lower than that in parental A549 cells, but that in G₂/M phase ratio was higher significantly (P<0.05).The expression of Notch1 had no marked change compared to A549 cell. Conclusions The radioresistance of the A549 cell subline is correlated with the irradiation program. The cell subline shows a different cell cycle distribution from their parental line. The cell cycle distribution has a close correlation with the expression of Notchl.